T180 more bibinfo

Lots of changes here. But I think it represents a good first step towards providing more bibliographic information for items. 

At a high level there is a new module `lp.ui.marc` which contains a mapping table that is used to augment the basic bib_data with information from the MARC record. The information is then used to populate the details tab in the item display.

I added a management command `get_test_records` which walks the database looking for MARC records that satisfy the mapping table. I used these as the basis for the new tests. Along the way I found it useful to add a view for the MARC as JSON, which is linked from the item view HTML.